Activation and energy transfers supporting potential peptide protometabolisms at the origin of living systems
Activation et transferts d’énergie supportant des protométabolismes peptidiques potentiels à l’origine des systèmes vivants
Résumé
Life on Earth constitutes a historical process that developed by complexification starting from chemical
systems. It is considered in this project that physico-chemical driving forces and contingency are responsible
of this process since its early beginning. Theoretical aspects will constitute both the starting point of this
project and a matter of investigation to contribute to a better understanding of the physical origin of
complexity. Within this perspective, the emergence of protometabolisms defined as networks of chemical
reactions proceeding under far from equilibrium conditions and involving nonlinear features and therefore
being capable of generating self-organisation (associated with a local decrease in entropy compensated by
the irreversibility of the overall process) is a key step for the origin of life. Chemical networks of this kind
must work as unidirectional sequences of reactions or preferably as unidirectional reaction cycles in which a
further process of positive chemical feedback would be capable of generating systems endowed with
autocatalytic properties and then behaving in a nonlinear way. Determining which pathways could have
constantly or repeatedly fed these systems with energy to maintain the far from equilibrium state is then
essential to understand how self-organisation could emerge. This approach is applied to the formation of
biopolymers capable of functional activities that is generally considered as a prerequisite for the origin of
life. Our original goal is to propose an overall scenario integrating the formation of peptides and other related
processes to build a network capable of giving rise to emergent properties related to the connections of the
different parts of the network. The project is aimed at understanding how peptides could be formed under
prebiotic conditions and how energy sources could have been coupled to peptide bond formation. But it is
not limited to this goal since random peptides made from racemic mixtures of amino acids are unlikely to
adopt definite structures needed for specific activity so that it will address the question of the emergence of
selectivity (and stereoselectivity) or that of improbable but dynamically stable states. Lastly the emergence
of translation at an early stage of evolution suggests that the chemistry of amino acids and peptides can be
coupled to that of an information carrier supporting the hypothesis of a peptide-nucleotide co-evolution. All
these topics will be experimentally investigated by monitoring the reactions through common methods of
analytical chemistry and organic chemistry (NMR, HPLC, MS, UV…).